Typically they do just fine with snails and bottom dwelling fish like cory cats and snails. Just be certain to get SEVERAL (3-5) cory cats as they are schooling fish and don't do well living alone. For a 5 gal. tank, you want to pick a small breed. Venezuelan pygmy corys (Corydoras habrosus) should do very well.

However, bettas are very individual and they have personalities all their own. Sometimes bettas do not tolerate any other living things in their space. I had one betta that I couldn't even keep a snail with as he would relentlessly attack anything that moved, even my finger. My current betta though lives with 5 otocinclus cats and doesn't care about them.

My best advice is to make sure you get the 5 gal. tank set up with your corys and your snail BEFORE you introduce the betta. They often will not attack fish that are already in a tank they are introduced to and can get along peacefully.

Do NOT put a male and female betta together unless you are planning to breed. Male bettas are very strictly life-long loners and will not tolerate their own kind except briefly at breeding time. They otherwise savagely attack any betta or anything that looks like a betta, male or female.

A few females can be housed together only if they are raised together. Otherwise they also are loners and will chase and fight off other bettas, male or female.

You can tell male and female bettas apart because only the males have those beautiful long, flowing fins. The females are drabber in color and have short fins.